Modern vehicles may be equipped with heating, ventilation, and air conditioning (HVAC) systems to control conditioned air supplied, for example, to the cabin of the vehicle. In some HVAC systems, a conventional compressor unit is driven by the main engine of the vehicle through a belt. When the HVAC system is activated, a mechanical clutch operates to engage the compressor to the main engine. When engaged, the speed of the compressor is dependent on the speed of the main engine, i.e., the rotational speed of the compressor is directly proportional to that of the main engine of the vehicle. Thus, the compressor output increases as the speed of the main engine increases. Conversely, the compressor output decreases as the speed of the main engine decreases.
As a result, the operating speed of the main engine may or may not correlate to a desired compressor output for conditioning air to a desired temperature. For example, when the main engine speed is relatively high, the compressor may be caused to over-cool the air supplied to the cabin of the vehicle.
Compressors driven by electric motors have been proposed to provide variable control of the compressor in vehicle HVAC systems. For example, U.S. Pat. No. 5,983,652 issued to Iritani, et al. describes an electric motor driven automotive air conditioner system having a condenser and an evaporator provided within an air duct. While the system of the '652 patent may provide an HVAC system using a compressor which may be variably controlled by controlling the electric motor, the system includes shortcomings. For example, the system of the '652 patent does not appropriately take into account the numerous variables associated with an efficient operation of an HVAC system. For example, the '652 patent does not address the problems associated with the build-up of ice on the evaporator component of the system.
Methods and systems consistent with certain features of the disclosure are directed to solving one or more of the problems set forth above.